1. Field of the Invention
The present invention relates generally to cellular telecommunications systems and methods, and specifically to providing a call back on busy feature to mobile subscribers.
2. Background of the Present Invention
Cellular telecommunications is one of the fastest growing and most demanding telecommunications applications today. There are an increasing number of supplementary services being offered by cellular network operators to further the desirability of cellular communications. For example, one such supplementary feature is the call back on busy feature, which enables a calling mobile subscriber, encountering a busy signal at the called subscriber, to have the call completed when the called subscriber becomes idle, without having to make a new call attempt.
The European Telecommunications Standards Institute (ETSI) has set forth certain standards for Implementing the call back on busy feature within cellular networks in the GSM 02.93 version 6.0.1 Technical Specification, which was released in 1997. In this Technical Specification, when a calling mobile subscriber encounters a busy indication at the called subscriber, the calling mobile subscriber can activate the call back on busy feature against the called subscriber.
Upon activation, the network retains the call information and informs the calling mobile subscriber that the call back on busy feature has been activated. When the activation of a call back on busy request is accepted, the network initializes a network-defined callback on busy duration timer. During the time period defined by the duration timer, the network constantly monitors the called subscriber for becoming idle by attempting call setups to the called subscriber.
If, before the expiration of the network retention timer, the network determines that the called subscriber has become idle, the network waits a short time in order to allow the called subscriber to make any necessary outgoing calls. If the called subscriber does not make any outgoing calls within this time period, the network automatically recalls the calling mobile subscriber and alerts the calling subscriber that the call is a recall to the called subscriber. When the calling mobile subscriber answers, the network automatically generates a call to the now idle called subscriber.
However, under the current standards, during the time that the called subscriber is busy, the network is spending unnecessary resources in retrying the call setup until the previously busy called subscriber becomes idle. In addition, the duration timer for retrying the call is set by the network, which does not allow the calling mobile subscriber to specify the maximum waiting period after which the call back is not attempted.
The present invention is directed to telecommunications systems and methods for allowing a calling mobile subscriber to activate a call back on busy feature and specify the maximum waiting period after which the call back is no longer attempted. In addition, during the call back process, the network does not spend unnecessary resources in retrying the call setup. This is achieved through changes in the processing and signaling mechanisms at the Mobile Switching Center/Visitor Location Register (MSC/VLR) nodes in the cellular network. Upon reception of a busy indication at the original MSC/VLR serving the calling mobile subscriber, the original MSC/VLR plays an announcement to the calling mobile subscriber to collect the time interval beyond which the network should cease to attempt the call back.
Upon reception of this subscriber-defined time interval, the original MSC/VLR sends a message containing calling subscriber identification information, an indication that the call back on busy feature has been activated and the subscriber-defined time interval over which the call back on busy feature is active to the destination MSC/VLR serving the previously busy called mobile subscriber. In response to receipt of this information, the destination MSC/VLR stores the received data in a database therein, initializes a timer with the subscriber-defined time interval and acknowledges reception of the information back to the original MSC/VLR. Thereafter, the original MSC/VLR releases the resources seized by the calling mobile subscriber, which allows the calling mobile subscriber to access other services while waiting for the call back to occur.
When the destination MSC/VLR determines that the previously busy called mobile subscriber has become idle, e.g., when a traffic channel for the called mobile subscriber is released, the destination MSC/VLR sends a call setup message to the original MSC/VLR, using the information stored in the database. An indication that the call setup message is a result of a call back requested by the calling mobile subscriber is also sent in the call setup message. The original MSC/VLR uses this indication to alert the calling mobile subscriber that the incoming call is a call back from the previously busy called mobile subscriber. Thereafter, a call between the calling and called mobile subscribers is established, as normal.
In an alternative embodiment, the called subscriber can be a wireline subscriber. In this embodiment, the original MSC/VLR sends the information to an end office associated with the called subscriber. When the end office determines that the called subscriber is idle, e.g., when circuits are released for the called subscriber, the end office sends the call setup message to the original MSC/VLR to establish a call connection between the calling mobile subscriber and the called wireline subscriber.